body {
    height: 100vh;
    width: 100vw;
    background-color: #34459e;
    margin: 0;
    padding: 0;
    display: flex;
    /*按列来排列*/
    flex-direction: column;
    /*主轴*/
    justify-content: center;
    /*交叉轴*/
    align-items: center;
}

.btns {
    margin-top: 10px;
    display: flex;
    /*主轴*/
    align-items: center;
}

.line-color-container {
    display: flex;
}

.img-print-screen {
    margin-top: 15px;
    width: 300px;
    height: 150px;
}
